Fabrication Of Energy Storage Devices Based On Graphite Felt Electrode Treated By Nitric Acid

Zinc-based batteries may be widely used in the future,because the lithium batteries will burn if they are damaged and they are difficult to recycle.Zinc-based batteries have little impact on the environment.At the same time,in order to meet the demands of future equipments that can be bent,Zn-Mn O₂ battery was tried to design into a flexible structure.A kind of hydrogel（PAAm）was made to act as the separator and electrolyte provider of the battery.The advantage of hydrogel is that it has a certain strength,which can hinder the growth of zinc dendrites and prevent battery from short circuiting.In addition,the hydrogel can lock the electrolyte in the colloid firmly,which makes the packaging of the flexible battery not leaked even if it is damaged.Finally,the quasi-solid electrolyte is not prone to spontaneous combustion,so it is safe.In this disseratation,the Mn O₂-based electrode was used as the battery cathode,which determines the battery performance.Graphite felt was used as the base material because of its own superiority,such as cheap price,corrosion resistance and flexibility.On the other hand,the defects of graphite felt are also very significant,such as limited specific capacitance,hydrophobic,which is difficult to the attachment of metal oxide.It is necessary to improve the disadvantages of PGF while retaining the advantages of the graphite felt as much as possible.A simple method based on HNO₃treating graphite felt was developed.Compared with the PGF,the treated graphite felt（TGF）has greatly changed in the increase of the specific capacitance.It was found that it had a lot to do with wettability,the number of oxygen-containing functional groups and the pore size distribution.Then the active material was loaded on TGF and its performance was tested.The flexible quasi-solid Zn-Mn O₂ battery built has achieved good performance and has great application prospects.There are four main parts of the experiment processes in this dissertation.Firstly,PGF was cleaned with organic solvents and deionized water to improve cleanliness.Concentrated HNO₃was used to activate PGF in a simple one-step method to obtain TGF afterwards.Then,Mn O₂ and Sn O₂ were loaded on TGF respectively to verify the synergistic effect between active materials and TGF.Finally,the electrode combining Mn O₂with TGF（Mn O₂/TGF）was applied to Zn-Mn O₂ flexible quasi-solid battery.The testing process in this article covers characterization and electrochemical testing.In order to study electrode characteristics,characterization methods include SEM,TEM,XRD,XPS,Raman,BET,FTIR,EDS and contact angle tests.Electrochemical tests include cyclic voltammetry（CV）test,galvanostatic charging and discharging（GCD）test and electrochemical impedance spectroscopy（EIS）test.It was found that the specific capacitance of TGF was 272 m F·cm^-2.The specific capacitance of Sn O₂/TGF reached 640 m F·cm^-2.The specific capacitance was 93%of the original after 5000 cycles.The specific capacitance of Mn O₂/TGF was 929 m F·cm^-2.Meanwhile,it could stay close to 88%after 10000 cycles,which was much better than those of Mn O₂/PGF and Sn O₂/PGF.The packaging structure of flexible quasi-solid zinc-ion batteries has been studied.The zinc foil acts as anode.The cathode of the battery is Mn O₂/TGF.The electrolyte is added 0.5 M Mn SO₄ into 2 M Zn SO₄.The hydrogel is used as the separator of the battery and the electrolyte is fixed in the colloid after ion exchange.GCD test was used to study the battery capacitor and the LANHE test system was used to test the battery cycle stability.It was found that the battery capacity was 1258(0.1m Ah·m^-2),and the battery capacity was 91%of the original after 1000 cycles.The energy density is 1812μWh·cm^-2 at a power density of 3.7 m W·cm^-2.It is considered that Mn O₂/TGF has great potential in Zn-Mn O₂ flexible quasi-solid battery.